西北干旱区不同下垫面反照率随太阳高度角变化的参数化方案

Parameterization Scheme about Albedo Changing with Solar Altitude Angle over Different Underlying Surface in Arid Areas of Northwest China

利用古浪非均匀近地层观测试验中仪器平行对比观测试验数据,首先详细地分析了三套不同型号辐射仪器(CNR4,Kipp&Zonen;PSP,Eppley;MS102,EKO)在荒漠均匀下垫面彼此之间观测辐射的差异;然后结合基本观测试验中西沙漠、东沙漠和农田站的晴天观测资料,基于乘法和加法关系分离影响因子的方法发展了干旱区不同下垫面反照率随太阳高度角变化的参数化方案,并检验了两种分离方法的普适性;最后对所发展的参数化方案与已有参数化方案在西沙漠、东沙漠及农田下垫面进行了对比。结果表明:(1)CNR4与PSP和MS102观测辐射数据相关系数在0.96以上,彼此之间观测短波辐射差异在6%以内,长波辐射差异在2%以内,净辐射差异在10%以内;CNR4与PSP观测值较接近,差异在5%以内,而CNR4与MS102观测值相差较大,差异在10%以内。(2)乘法关系分离影响因子方法的普适性较好。(3)与已有参数化方案相比,本文所发展的参数化方案能更加合理地刻画干旱区不同下垫面反照率随太阳高度角的日变化关系。

Using the data attained by the instrument parallel experiment of Gulang Heterogeneous Underlying Surface Layer Experiment over the uniform desert land surface, a detailed analysis of observational radiations was made to value the three different types of radiation instruments （CNR4, Kipp＆Zonen; PSP, Eppley; MS102, EKO） at first; and then using the data observed over western, eastern desert and cropland stations in sunny days of the basic observation, the parameterization schemes about surface albedo changing with solar altitude angle were~ developed by two separation methods of plus and multiplication over different underlying surface in arid are- as, and their universality on different land surfaces were checked; finally, the parameterization scheme developed in this paper were compared to the several existing parameterization schemes over western, eastern desert and cropland underlying surfaces. The results show that： （ 1 ） The correlation coefficients between the radiation ob- served by CNR4 and the radiations observed by PSP and MS102 are more than 0.96, the difference of observa- tional shortwave radiation is less than 6%, the difference of observational longwave radiation is less than 2%, the difference of net radiation is less than 10% ; the radiation observed by PSP is more close to that observed by CNR4, the difference of them is less than 5%, while the radiation observed by MS102 is more bias to that ob- served by CNR4, the difference of them is less than 10%. （2） Multiplication separation is universal. （3） Com- pared to several existing parameterization schemes, the parameterization scheme developed in this paper is better in portraying the diurnal variation of surface albedo with solar altitude angle over different underlying surface land in the arid areas.